An ordinary toilet is arranged with a tank in which flushing water for cleaning the toilet bowl is stored and discharged into the toilet bowl. Filth present in the toilet bowl is flushed directly through a drain and conveyed to the outside of the toilet bowl by the flushing water under the pressure thereof. An alternative arrangement has a generally-known siphon flow conduit which is formed so as to curve upward above the toilet bowl and, when the flushing water is discharged, the flushing water fills the siphon flow conduit up to the curved part, generating a siphon effect. With the addition of the siphon effect, filth is drawn into the outlet and conveyed to the outside of the toilet bowl. In this case, the flushing water in the bowl part is conveyed together with the filth, thereby also cleaning the toilet bowl. Usually, for the flushing water in the tank to thus convey the filth and also clean the toilet bowl, ten or more liters of water needs to be stored at a height of around 30 cm to impart the necessary potential energy to the stored water.
However, in recent years the increasing population concentrations in major cities and global irregularities of climate and weather have made it difficult to provide stable supplies of water for everyday use. This has caused local authorities and governments to impose restrictions on the use of water in a number of areas, or call for less water to be consumed. Defecation toilet bowls have not been exempted. In the United States, for example, in 1994 the government changed the regulations to lower the volume of water used to flush a toilet bowl from 3.5 gallons (about 13 liters) to 1.6 gallons (about 6 liters), and measures aimed at consuming less water are also being imposed by Taiwan and Singapore. In Japan, also, ways are being studied to reduce water consumption, on a city, town and village basis.
A common method of economizing on water consumption is to place a brick in the flushing water tank to reduce the visible amount of water that is stored. However, this is not really an adequate answer, since the result is that there is not enough water to properly clean the toilet bowl.
A number of proposals have been made in response to the need to economize on water consumption, including JAPANESE PATENT LAYING-OPEN GAZETTE 54-18137 and JAPANESE PATENT PUBLICATION GAZETTE 6-99952. These disclosed techniques comprise a subtank which is to be installed inside an existing flushing water tank so as to store the flushing water applied with about the same degree of pressure as the water service supply pressure. When the toilet bowl is being flushed, the subtank water thus subjected to pressure giving it energy equivalent to the water service supply pressure, is discharged into the toilet bowl. Although this enables the amount of flushing water to be decreased, the size of the flushing water tank has to be increased by a volume enough to allow the subtank to be accommodated. So that, there have been some cases wherein such toilet as above cannot be installed in small toilet rooms. Also, in the case of low-silhouette type toilets wherein the water tank is positioned lower down to allow it to be integrated with the toilet bowl, design constraints mean that it is difficult to make the water tank large enough to accommodate a subtank. Moreover, when the flushing water under pressure in the subtank is just about enough to clean the toilet bowl, it can take quite a time for the flushing water to fill the subtank. As such, when the toilet is being consecutively used and flushed by a number of users, each user has to wait for the subtank to fill.
JAPANESE PATENT LAYING-OPEN GAZETTE 5-311719 discloses another technique. The technique comprises a horizontal waste trap, wherein the horizontal conduit has an upward bend before connecting with the drain outlet, to provide a water pool part in front of the drain outlet that serves as a seal. Air in the space between the sealing water in the toilet bowl and said water pool part is sucked by the negative pressure generated when the water in the sealed tank is discharged into the toilet bowl. This negative pressure is designed to drain out the air in the trap, generating a siphon effect that enhances the efficiency with which filth is drained out. The reason for providing an air space over the water pool part is that, were not for the air space, the suction of the negative pressure would cause not only the pooled water but also the water in the toilet bowl to drain out through the drain channel on generation of a negative pressure on the drain channel side, allowing foul odors to flow back into the toilet bowl from the drain channel.
However, this technique that utilizes negative pressure in the tank requires the tank to have a leak-tight structure. Even with the air passage provided as described above, since the downstream side of the sealing water and the tank are connected, foul odors may still flow back into the tank, so it is necessary to provide a separate structure to prevent that.
Moreover, in the midst of calls for water economy, the high-class image projected by the low-silhouette type toilet is increasing the popularity. The low positioning of the flushing water tank on such toilet bowls reduces the potential energy of the water in the tank. This has led to arrangements such as the one disclosed in JAPANESE PATENT LAYING-OPEN GAZETTE 60-203748 in which, to compensate the low potential energy, a vortex jet outlet is provided so as to produce a vortex in the toilet bowl. However, to adequately clean a low-silhouette type toilet still requires more flushing water than a conventional toilet.
The present invention has been conceived to solve the above-specified problems and has an object to economize on water consumption while maintaining cleaning performance.
Another object of the present invention is also to provide a toilet, particularly a low-silhouette type toilet, which economizes on water consumption while maintaining cleaning performance.